Married for 20 years, Ai lives alone with her son, Hideyuki, while her husband has been working apart from the family for the past five years. Feeling lonely in her husband's absence, Ai begins an affair. By chance, Hideyuki discovers his mother's infidelity. But Hideyuki has long viewed Ai not just as his mother, but as a woman he desires. Keeping his feelings hidden until now, he finally confesses his love to her. To his surprise, Ai warmly accepts his emotions, and the two embark on a forbidden relationship. Driven by intense passion, they plunge into a deep, taboo bond that transcends the boundaries of mother and son.